Carrier telegraph system



March 22, 1932. THQRP CARRIER TELEGRAPH SYSTEM Original Filed- Aug. 10, 1928 177 other Receiving INVENTOIR ATTORNEY Patented Mar. 22,1932

PATENT QFFIGEZ 1 g VAUGHN P. THjOB-P, ornrvnn NEW JERSEY, nssrsnon. TO AMERICAN rnnnrnonn AND TELEGRAPH, company, A' CORBORATION'OF NEW YORK CAIBRIEIR TELEGRAPHJSYSTEM I Application filefd rA'ngust 1.0, 1928,'Seria,1 N'o. 298,738. Renewed August 12,1981. I,

This invention} relatesto the art of tele graph communication, and discloses a half. duplex carrier telegraph systemin which the same carrier frequency; is utilized for the transmission of signa s in both directions over a given carrier channel. I I It IS the general practice, lncarrier current telegraphy, to use distinct frequencies for transmission in the two, directionsover' a given channel. There are a number of rea -t sons'for this among which the jfollOWing may bementioned as being probably the; more important. Where the. fullduplex method of;

operation is desired, .the terminal apparatus is much simplified by theuse of separatefre quencies transnnttmg and rece ving since, by

the insertion of suitable. band pass filters, i nterference. between thetransmitting and re-' ceiving equipment at the same end of a circuit maybe eliminated. The use of separate frequencies transmitting and receiving simplifies the amplificationof the telegraph currents at through repeater .pointsflocated at intermediate points. along the telegraphline. In this case, theinsertionof snitable. bang1 pass filters in series withthe. repeater elements amplifying in opposite. directions eliminates the necessity for inserting hybrid coils inthe circuitat the repeater point for; purposes of balance in ordernto, eliminate-singing. A.-

third instance making desirablethe use of distinct frequencies for transmittin gand re.-. ceiving over a carrier channel, occurs-where two similar carrier systems. are operating over conductor pairs of open wire hnellocated on thev same pole line. Under these condi-s tions, if the same trequency were used, for transmitting and. receiv ng, thesignals trans? mitted from one terminal over conductor p311 A, say, would get over into conductor pair'B and affect the carrier equipment at the .ter-. minal in question operating at ,the same free.

quency over the latterconductor pair.

Although for the reasons outlined above it is, in general, desirable.towuseseparate frequencies for transmittingand receiving over a given carrier telegraph channehf instances occur in which the above difiiculties are; not encountered, and hence in snchwcases the use of separate frequencies transmitting and re,

'ceivi'ng is not required. For example, where system. A'short section of submarine cable containing vonly one pair of conductors for use in carrier current telegraphy would oiier an example of a situation where thetwo )latter difficulties wouldbe eliminated.

A carrier current telegraph system adapted to utilize the same frequency for transmitting and receiving over a given channel isdis closed in the present invention, for use where practicable. l The system is best understood by reference to the drawing, which shows in schematic form the terminal equipment at a I giveno'fiice both transmitting and receiving fora'single channel, together with a sub! scribers loop extending to atsubscribersstation with control equipment at the subscribers station for transmitting and receiv-f;

ingthesignals. I I r Referringto the drawing, the equipment 101-, cated to the left'ofthe Vertical line mm is located at the central .ofiice. This equipment is associated with'the carriercircuit 16 which extends to the distant poin. At the subscribersstation23 is located a sendingkey l8 for controllingthe transmissiongof carrier impulses to the distant point, and, the sounder mechanism voperatingnnder control of the carrier signals received from the distant point. The subscribers station is connected to the equipment at the central oflice ,over the lo'op17. It is understood,of course, thata printing. telegraph transmitting and receiving set or other D. C. telegraph meanscould.

be used instead of :the. sending hey 18 and sounder 4 which are indicated at lstaw tion23. f I At'the central olfice the equipment'for, transmitting signalsto the distant point.com-. prises the oscillator 5 for generating a. single frequency carrier current,-a band pass filter 6; for passing the. generated current and an amplifier?fora'mpligfying thesame. The sig- I na-l modulated carrier current, is applied to the carrier line 16 through hybrid coil 8. The

iii

balancing network 11 matches the impedance of the line 16 to prevent the transmitted current from entering the receiving equipment located at the same central ofiice.

The receiving equipment is associated with the lowest winding of coil 8 andcomprises the high pass filter 9 which serves to prevent the voice frequency telephone currents on the slam-s line circuit from entering the receiving equipment, amplifier 10 to ampl fy the received carrier current, a band pass filter 12 to permit the proper frequency to enterthe receiving equipment, detector 13 for rectifying the receivedcarrier current and relay 3 operated by the current thus detected.

The circuit opera"'on for the sending signals will first be considered. With key 18 down as shown,relays 1 and 2 are operated against their marking contacts M. This ocours as a result of current flowing from plus battery 22 over the lower conductor of loop 17 through sounder 4, sending key 18, upper conductor of loop 17, upper or line windings of polar relays 2 and 1 in series, over lead 25, through the marking contact M of relay 3 to ground through minus battery 21. This current, in flowing through the line windings of relays 1 and 2, holds the armatures thereof against the marking contact M. A second Vi hen, however, current in the line windings is interrupted, the current in the auxiliary windings causes relays 1 and 2 to move against their spacing contacts.

' With key 18 down, as shown, operation of relay 2 against its marking contact, as'explained, the circuit containing oscillator 5 is opened at the contacts of relay 2, with the result that no carrier current is transmitted outover the line 16. hen key 18 is opened, however, relays 2 andl immediately move against explained above.

The operation of relay 2 against its spacmg contact closes the circuit 5 and thus causes the containing oscillator carrier current to be applied to line 16 through filter 6, amplifier 7 and hybrid coil 8. At the same time, the operation of relay 1 against its spacing contact opens the receiving circuit at the contacts of relay 1, and thus prevents any possibility of the transmitted current getting into and affecting the receiving detector 13. When, of course, key 18 is depressed again, it again completes the causing the their spaclng contacts, as

circuit through the line windings of relays 1 and 2, permitting current to flow therethrough and reoperate the relays against their marking contacts, in the manner explained.

It should be noted here that when key 18 is opened, operating relays 1 and 2 against their spacing contacts, the receiving circuit is opened atthe contacts of relay 1 before the sending circuit is closed at the contacts of relay 2. Again, when key 18 is later depressed, r-eoperating relays 1 and 2 against their marking contacts, the operation of relay 2' opensthe circuit for transmitting the carrier current before the receivingcircuit is closed by the operation of relay 1. It will thus be seen'thatthere is a certain operating margin which insures that the receiving circuit will always be open while carrier current is being transmitted from oscillator 5, thus insuring that the signaling current transmitted from a given oiiice will not ahect the receiving equipment at such oilice.

For the reception of signals from the distant point, key 18 is left closed continuously. The'carrier signals incoming over circuit 16 flow through hybrid coil 8, through the high pass'filter 9, through the amplifier 10, through the band pass filter 12, transformer 19 and detector 15. The receiving circuit of course, completed through the contacts of relay 1 since this relay is operated against its marking contact while key 18 is down, as ex plained. The incoming carrier signals op crate relay 3 against its spacing contact S. Normally, with noincoming slgnahng currents th1s relay 1s held agalnst its marking contact by current from grounded battery 21' through the lower or auxiliary winding of relay 3 to ground. The grid of detector 13 is so biased that normally no current flows inthe upper or line winding of relay 8.'

When, however, carrier current is impressed upon the detector, a sufiicient plate current flows in the line winding of relay 3 and in proper direction to operateit against its spacing contact. Relay 3 thus follows the incoming fcarrier signals and is operated againstits spacing contact while carrier current is being received. These incoming carrier signals cause the operation of sounder 4 at subscribers station. 23 as follows. With no" carrier current incoming, current flows from positive grounded battery 22, over the lower conductor of loop 17, through sounder 4, key 18, upper conductor of loop 1?, line windingsof relays 2and 1 in series, over lead 25, through the marking contact of relay 3 to ground through negative battery 21 as er;- plained. This current holds the sounder 4 operated to its marl ing position. When, now, a carrier signal incoming over the line 16 affects detector 13 and causes relay 3 to operate against its spacing contact, positive battery 20 is substituted for negative battery 'ing signal incoming over,

will bearranged as shown infthe drawing,

of course,:a spac-V line 16, will flow through the receiving equipment: and cause. relay 3 to be operated against its spacing contact. Theoperationof relay 3, as was explained above, substitutes positive battery 20 for negative battery 21'. The positive battery20 opposes the positive battery 22 and thus prevents current flowing. through sounder 4, causing the same to be operated The break signal which is,

against its spacing contact. Also, the. oppos- 7 ing batteries prevent current from flowing through the linewindings of relays 1 and 2.

These relays, are notoperated against their spacing contacts in; this instance, however, due to the fact thatthedirection of'current flow through the auxiliary windings has been reversed, due to the substitutionof positive the sending circuit is, no longer under con-H trol of station 23, due to-the fact that with,

battery 20 for negative battery 2L The negative battery 21, it will be remembered from.

the above explanation, normally-supplies current through the auxiliary windings-of relays 1 and 2, which tends to move these relays against their spacingcontacts, and-will do so when the currentrin the line {windings is interrupted. In the present'r'instance, however, current through the auxiliary windings is supplied from positivebattery 20 which reverses the direction of normal current :flowthrough the auxiliary windings. and thus tends to holdthese relays; againsttheir mark ing contacts, and will do so when, as; in the present instance, no current flows inthe line 1 windings. Thus,. it will "be seen that, due to the substitution of battery 20 for battery 21 in the manner explained, the operation-of key 18 either open or closed, no current flows in the, subscribers loop 1 7"and' hence relays 1 and 2 and sounderl remain inoperative and.

do not follow 18.-

the further operations of, key Had key 18-been open when thebreak sig nal was transmitted from "the distant point, relay 1. would,;of course,- have: been operatedagainst its, spacing contact,. thus openingthereceiving; circuit and preventing the break; signal from affecting the detector"13 or. relay 3.; l The breaksignal would be, therefore, inc-J brid coil and controlled effective until key 18- was-closed, at which time the, sequence of operations described the immediately preceding paragraph woul ak P ac V What is claimed is z" a I o 1- n a a ier nt t leg p ys m n, combination a line extending from affirst to a second oflice', a loop extendingfromthe first office to a local subscribers station and terminated ii -telegraph sending and receiving means thereat, sending relay means ass sociated with said loop at the first office responsive to saidsubscribers sending means, a sending circuit controlled in accordance with the operation ofsaid sending relay means, an oscillator circuit individual to and asseciated with said sending circuit, for applying thereto pulses of signaling current of a predetermined frequency for transmission oversaid line to the second ofiice, filter means individual to said sending circuit, means at the first oflice associated with said line for receiving from the second offioe pulsesof'signalingcurrent of said, predetermined frequency comprising, a filter for passingcure rent of said frequency, a detector associated therewith for rectifying the same, receiving relay means in the detector output responsive to said rectified current pulses for apply-' ing alternately plus and minus battery to the loop to operate said ,subscribers receiving means, and meanscontrolled by said sending relay meansfor opening the receiving circuit at the first office while signaling currentof said frequency is being transmitted there-- from, and means for, preventing the operation of said sending relay means at the first ofiice and said subscribers receiving means while steady .signalingcurrent is being receivedfromv the second ofiice.

combination, a line extendingwfrom a certain point to a central ofiice, a balancing network associated with the line at said ofiice, a hybrid coil having input and output terminals interposed between the line" and network, a loop extendingfrom said ofiice to a subscriber s station, a telegraph sending key and sounder associated with the loop thereat, polar sending and control relays associated with the loop at the'central ofiicerresponsive to said sending key operation, a sending circuit associated with the input terminal of said hyby said sending relay,,an oscillator and an'oscillator circuit individual to and associatedwith said sending circuit for applying thereto pulses of signaling current of a predetermined frequency for transmission over saidline to said certain point, a.;filter circuit connected to, said hybrid coil output terminals for passing pulsesof. signaling current of said. predetermined fre-- i quency transmitted fromsaid certain point,

detector means connectedtosaid filter for,

rectifying said-currentpulses,,a receiving reg ism 7 0. 2. In a carrier current telegraph system in lay in the detector output'responsive to said rectified current for applying alternately plus and minus battery to saidloop to operate said telegraph sounder, means forapplying one-of said batteriesto the windings of said sending and control relays andto said sounder to prevent their operation while steady signaling current is received from said certain point,

i and means controlled by said control relay to prevent operation of the receiving relay by current transmitted from said oscillator.

3. In acarrier current telegraph system in combination, a line extending from a first to a second oiiice, associated with said line at each said oiiice the following: a balancing network to simulate the line impedance, a hybrid coil with input and output terminals interposed between line and network, a subscribers' loop extending from the central offlee to a subscribers station, telegraph sending and receiving means associated with the loop thereat, a sending relay, associated with the loop at the central ofiice responsive to said subscribers sending means, means controlled in accordance with the operation of said sending relay for applying to said hybrid coil input terminal pulses of signaling current of a predetermined frequency for trans= mission to the distant office, a receiving cir- V cuit connected to the hybrid coil output terminals comprising a filter for passing signaling current of said predetermined frequency transmitted from the distant oifice, a detector connected to said filter for rectifying said current, a-receiving relay in the detector output responsive to said rectified current, and means controlled thereby for applying alternately plus and minus battery to said loop to operate said subscribers receiving means, relay means associated with said loop responsive to said subscribers sending means for opening said receiving circuit at a given oifice while signaling current is being transmitted from such oific-e, and means controlled by the receiving circuit at a given office to hold the sending and control relays at such oiiice and the receiving means at the subscribers station connected thereto inoperative, while steady signaling current is re ceived from the distant oiiice.

4. In a telegraphsystem, 1n combination,

a telegraph circuit extending from a first point to a second point, a sending key and a receiver at each of said points, a sending cir cuit at each of said points adaptedto be effectively associated with said telegraph circuit in accordance with the operation of the sending key, a generator circuit individual to and associated with said sending circuit for applying to said sending circuit pulses of signaling current of a predetermined frequency for ill'iLIlSHllSSlOll to the other point, filter means individual to sald sending circuit, a receiving system at each of said points for receiving thesignalingcurrent of said predetermined frequency, and means at each of said points controlled by the operation of the sending key thereat for rendering the receiving circuit thereat non-responsive to the transmitted signaling current while signaling current ofsaid predetermined frequency is being transmitted therefrom. I

5. In a telegraph system, in combination, a telegraph circuit terminating at a telegraph station,balancing means associated with said telegraph circuit, a sending key and a receiver at said station, a sending circuit at said station'controlled in accordance with the operation of said sending key, a generator circuit individual to and associated with said sending circuit for applying to said telegraph circuit pulses of signaling current of a predetermined frequency for transmission to a distant point, a receiving circuit at said station for receiving signaling current of said predetermined frequency, and means at said stationcontrolled by the operation of said mitted from said station.

6. In a telegraph system, in combination, a telegraph circuit extending from a first station to a second station, a telegraph receiver-located at each station, a sending circuit at each station controlled by the operation of asending key, an oscillator circuit in-- clividual to and associated with said sending circuit for-applying to said sending circuit pulses of signaling current of a predetermined frequency for transmission to the other station, a filter individual to said sending circuit, a receiving circuit at each station adapted to receive signaling current of said predetermined frequency from the other station, and'meansateach station for rendering the sending circuit thereat ineffective for the transmission of signals and for preventing the operation of the receiver thereat while steady signaling current of said predetermined frequency is being received from the other-station. a

7. In a telegraph system, in combination, a telegraph circuit extending from a first station to a second station, a telegraph receiver located at each station, a sending circuit at predetermined frequency is being trans frequency for transmission over said telegraph circuit to the other station, a receiving circuit at each station adapted to receive spacing. signals of said predetermined frequency from the other stat-ion, said receiving circuit being balanced with respect to said sending circuit, means at each station controlled bythe operation of the sending key thereat 'for rendering thereceiving circuit thereat 'IlOIlIBSPOIlSlVQ, to signaling current while spacing signals of said predetermined frequency are being transmittedtherefrom,

and means at each station for rendering the sending circuitthereat inefi'ective for the i in accordance with theoperation of said sendtransmission of signals and for preventing the operation of the receiver thereat while" steady spacing current of said predetermined frequency is being received fromothe other station. v

8. In a'telegraph system a telegraph circuit extending to a telegraph station, a sending key and a receiver at said station, a sending circuit at said station adapted to beeifectively associated with said telegraph circuit ing key, a generator circuit individual to and associated with said sending circuit for applying'signaling current to said sending) circuit for transmission to a distant point, a

filter individual to said sending circuit, a"

receiving circuit at said station for receivingsignaling current, and means at said station controlled by the operation of said sending key for renderingsaid receivingcircuit non-responsive to thet'ransmitted signaling current while si naling current is being transmitted from said station. i

9. In a telegraphsystemia telegraphcir;

cuit extending froni'a first station to a sec-- ond station, balancing means associated with said tel-egraphcircuit at each St&l31011,2t,t8l6

graphreceiver located at each station,- a send ing circuit at each stationcontrolled by the operation of a sendingkey, a generator cir-r, cuit'individual to and associated ,WltlISLld sending circuit for applying signaling current to said telegraph circuit for transmis sion to the other station, a receiving circuit at each station adapted to receive signaling current from the otherstation, and means at each station for rendering the sending circuit thereat ineifective for'the transmission circuit for applying spacing signals to said sending, circuit for transmission over said telegraph circuit to the other station, a filter individual to said sending circuit, a receiv- I ing circuit at each station adapted to receive spacing signals'froin the other station, means at each station controlled by the-operation,

of the sending key thereat for rendering the receiving circuit thereat non-responsive to the transmitted signaling currentwhile spacingsignals are being transmitted therefrom,-

and means, at each station for rendering the sending circuit thereat inefiective for the transmission vof signals and for preventing the operation of the receiver thereat while steady spacing current is being received from. i

the otherstation. c 11. In atelegraphsystem a telegraphcircuit extending .to a telegraph station, sending means and a receiverat each station, relay means at said station controlled in accordance withthe operation of said sending 7 means, a sending circuit controlled in accordancewith the operat on of said relay means for applying signaling current to said tele- U graph circuit for transmission to a distant point,a filter circuit individual to said sends ing circuit, a receiving circuit at said station for receiving signaling current, means for preventing the signalingcurrent in said sending circuit from being transmitted to' said receiv ng circuit, and means controlled in accordance with the operation of said relay .means for rendering said receiving circuitjnon-responsive to thetransmittedsignaling current while signaling current is being transmitted from said station. v

12. In a telegraph'system a telegraph circuit extending between two stations, a send- 95 ing circuit at each station adaptedtobe associated with said telegraph circuit, a source of signaling current and a circuit therefor individual to and associated with said sending circuit at each station, filter means in-. odividual to said sending circuit, sending as i means and a receiveryat each station, a receiv ing circuit associated with said telegraph circuit at eachstation, and means at each station controlled intaccordance with the 0131; eration of the sending means thereat for rendering the receiving ,CIIClllt thereat non-re sponsive to signaling current and after a preios determined interval of time'for associating I the sending circuit thereat with said telegraph circuit, said means also being adapted to dis-associate said sending circuit from said telegraph circuit in response to the further operation of said sending means and after a predetermined interval of time to render said receiving circuit responsive to the signaling current.

In testimony whereof, I have signed my name to this specification this 8th day of August 1928;

" VAUGHN P. THORP. 

